1. Field of the Invention
The present invention relates to an electron discharging apparatus and a method of manufacturing the apparatus. More particularly, the present invention relates to an electron discharging apparatus which may be employed for a display apparatus or an image-pickup apparatus, and, also applicable to such an electron beam exposure apparatus and an electron microscope as well.
2. Description of the Related Art
As was disclosed in the U.S. Pat. No. 4,303,930 (based on the Japanese Patent Laid-Open Publication No. SHOWA-56-15529/1981 and the other Japanese Patent Laid-Open Publication No. HEISEI-1-45694/1989) for example, in such a semiconductor apparatus substantially constituting a cold cathode, inverse-directional bias is applied so that avalanche multiplication of charged carrier can be attained. In this case, a certain electron can gain a thermal energy exceeding work function of electrons. In such a semiconductor apparatus, discharge of these electrons is easily executed by way of providing an accelerating electrode or a gate electrode on an insulating film formed on the main surface of the semiconductor apparatus. An aperture portion is formed at a position of an electron-discharging area of this insulating film. Discharge of electrons is more easily executed by providing a certain material capable of lowering work function of electrons on the surface of a semiconductor apparatus at the position of the electron discharging area.
Referring to a schematic cross-sectional view shown in FIG. 9, an example of a conventional electron discharging apparatus is described below.
As shown in FIG. 9, a conventional semiconductor substrate 110 is formed with a p+ type silicon substrate 111 and a p-type epitaxial layer 112 formed thereon. A p+ area 113 is formed in the p-type epitaxial layer 112, and, an n++ area 114 is formed on an upper layer whereby forming a pn-junction 115. Further, an n+ area 116 linked with the n++ area 114 is formed on an upper layer of the p-type epitaxial layer 112. An insulating film 121 is formed on the above-referred semiconductor substrate 110, and, an accelerating electrode 131 is formed on the insulating film 121. Further, an insulating film 141 is formed by covering the accelerating electrode 131.
Further, a connecting hole 122 connecting to the n+ area 113 is formed through the insulating film 121. An extraction electrode 132 connecting to the n+ area via the connecting hole 122 is formed. Further, another connecting hole 142 connecting to the accelerating electrode 131 is formed through the insulating film 141. Further, another extraction electrode 132 connecting to the accelerating electrode 131 is formed through the insulating film 141, and another extraction electrode 133 connecting to the accelerating electrode 131 is formed through the connecting hole 142. Further, a protecting film 143 is formed by covering the accelerating electrode 131 and the extraction electrodes 132 and 133.
Further, an aperture portion 125 for discharging electrons is formed through the protection film 143, the insulating film 141, the accelerating electrode 131, and the insulating film 121. Further, another aperture portion 144 for wire-bonding is formed through the protecting film 143 on the extraction electrode 133.
In order to maximize function of an electronic tube with emitted electrons by applying a voltage to the accelerating electrode utilized for a conventional electron discharging apparatus, structural relationship between an electron discharging surface and the accelerating electrode must be considered. However, in a conventional electron discharging apparatus based on a cold cathode structure, a pn-junction being the basis of the cold cathode structure is formed on a surface of a silicon substrate and an insulating film is formed on the pn-junction with using a planer process. Accordingly, there is such a critical problem that electrons can not fully be accelerated because of a remote distance between the electron discharging portion and the accelerating electrode. Further, in such a conventional electron discharging apparatus based on the conventional cold cathode structure, structurally, because of insufficient exposed area size of the accelerating electrode with respect to the electron discharging portion consisting of a pn-junction, acceleration of the discharged electrons may not be fully accomplished.
In order to fully solve the above problems, the present invention provides a novel electron discharging apparatus and a method of manufacturing the electron discharging apparatus.
A first electron discharging apparatus according to the present invention comprises the following:
a pn-junction formed on the part of the surface of a semiconductor substrate;
an insulating film formed on said semiconductor substrate;
an aperture portion formed through said insulation film on said pn-junction; and
an accelerating electrode formed on said insulating film so as to surround the periphery of said aperture portion;
wherein said accelerating electrode is formed so as to project its inner edge portion into said aperture portion. In the first electron discharging apparatus according to the present invention, inasmuch as the above-referred accelerating electrode is formed by way of projecting its inner edge portion into the aperture portion area, a lateral surface and the bottom surface of the accelerating electrode facing the aperture portion respectively extended into the aperture portion area. Accordingly, the accelerating electrode is provided with a greater exposure area with respect to an electron discharging portion consisting of a pn-junction than that of such an accelerating electrode provided for any of conventional electron discharging apparatuses. Because of this, electrons discharged from the pn-junction are fully accelerated.
A second electron discharging apparatus according to the present invention comprises the following:
a pn-junction formed on the part of the surface of a semiconductor apparatus;
an insulating film formed on said semiconductor substrate;
an aperture portion formed through said insulation film on said pn-junction;
and an accelerating electrode formed on said insulating film so as to surround the periphery of said aperture portion;
wherein said accelerating electrode is formed into a substantially L-shaped configuration at a cross-sectional plane.
In the second electron discharging apparatus according to the present invention, inasmuch as the above-referred accelerating electrode is formed into a substantially L-shaped configuration at a cross-sectional plane, the substantially L-shaped vertical-wall portion of the accelerating electrode is formed facing the aperture portion area, and thus, exposure area of the accelerating electrode against an electron discharging portion consisting of a pn-junction becomes greater than that of such an accelerating electrode provided for any of conventional electron discharging apparatuses. Because of this, electrons discharged from the electron discharging portion consisting of a pn-junction are fully accelerated.
A third electron discharging apparatus according to the present invention comprises the following:
a pn-junction formed on the part of the front surface of a semiconductor substrate;
an insulating film formed on said semiconductor substrate;
an aperture formed through said insulating film on said pn-junction; and
an accelerating electrode formed on said insulating film so as to surround the periphery of said aperture portion;
wherein said accelerating electrode is formed into a substantially inverse L-shaped configuration at a cross-sectional plane.
In the third electron discharging apparatus according to the present invention, inasmuch as the accelerating electrode is formed into a substantially inverse L-shaped configuration, the accelerating electrode is provided with a greater exposure area with respect to an electron discharging portion consisting of a pn-junction than that of such an accelerating electrode provided for any of conventional electron discharging apparatuses. Because of this, electrons discharged from the electron discharging portion consisting of a pn-junction are fully accelerated.
A first method for manufacturing an electron discharging apparatus according to the present invention comprises the following steps:
a step of forming a pn-junction on the part of the surface of a semiconductor substrate;
a step of forming an insulating film on said semiconductor substrate;
a step of forming an aperture portion through said insulation film on said pn-junction; and
a step of forming an accelerating electrode on said insulating film so as to surround said aperture portion; wherein said method further comprises a step of removing said insulating film facing said aperture portion below said accelerating electrode so as to dispose said accelerating electrode into the state where inner edge portion of the accelerating electrode is projecting into said aperture portion area.
Inasmuch as the above-referred first method comprises a step of removing said insulating film facing an aperture portion below the accelerating electrode so as to dispose the accelerating electrode into the state projecting itself into said aperture portion, a lateral surface and the bottom surface of the accelerating electrode facing the aperture portion respectively extend themselves against the aperture portion area. Accordingly, the accelerating electrode is so formed that an exposure area with respect to an electron discharging portion consisting of a pn-junction becomes greater than that of such an accelerating electrode provided for any of conventional electron discharging apparatuses. Because of this, the inventive accelerating electrode enables electrons discharged from the pn-junction to be accelerated to full extent.
A second method for manufacturing an electron discharging apparatus according to the present invention comprises the following steps:
a step of forming a pn-junction on the part of the surface of a semiconductor substrate;
a step of forming a first insulating film on said semiconductor substrate;
a step of forming an electrode film for forming an accelerating electrode on said first insulating film;
a step of forming a second insulating film on said electrode film;
a step of patterning said second insulating film and said electrode film;
a step of removing said second insulating film and said electrode film on said pn-junction to form an aperture portion through both films;
a step of forming a side-wall electrode on lateral wall of said aperture portion to enable said side-wall electrode to be connected to said electrode film;
a step of forming an accelerating electrode by utilizing said electrode film and said side-wall electrode; and
a step of extending said aperture portion after opening said first insulating film formed on said pn-junction.
By executing the above-referred second manufacturing method, inasmuch as a side-wall electrode to be connected to an electrode film is formed on a lateral wall of an aperture portion and then an accelerating electrode is formed by applying an electrode film and said side-wall electrode, the accelerating electrode is formed into a substantially L-shaped configuration. And yet, inasmuch as the side-wall electrode corresponding to the vertical wall portion of the substantially L-shaped accelerating electrode faces the aperture-portion side, the accelerating electrode is provided with a greater exposure area than that of such an accelerating electrode provided for any of conventional electron discharging apparatuses. Because of this, the formed accelerating electrode enables electrons discharged from the above-referred pn-junction to be accelerated to full extent.
A third method for manufacturing an electron discharging apparatus according to the present invention comprises the following steps:
a step of forming a pn-junction on the part of the surface of a semiconductor substrate;
a step of forming a first insulating film on said semiconductor substrate;
a step of forming a dummy pattern on said first insulating film above said pn-junction;
a step of forming an electrode film for forming an accelerating electrode by way of covering said first insulating film with said dummy pattern;
a step of forming a leveled insulating film on said electrode film;
a step of etching back said leveled insulating film and selectively removing said electrode film on said dummy pattern;
a step of forming an accelerating electrode by way of patterning said electrode film;
a step of removing said dummy pattern before forming said aperture portion in said accelerating electrode; and
a step of opening said first insulating film on said pn-junction before forming said aperture portion via extension thereof.
Inasmuch as the above-referred third method according to the present invention comprises serial steps consisting of a step of forming an electrode film necessary for forming an accelerating electrode by way of covering a dummy pattern, a step of forming a leveled insulating film on said electrode film, a step of etching back the leveled insulating film, and a step of selectively removing the electrode film on said dummy pattern, the electrode film is formed into a substantially L-shaped configuration at a cross-sectional plane. Further, inasmuch as the third method comprises a step of removing a dummy pattern in order to form an aperture portion, vertical-wall portion of the substantially L-shaped accelerating electrode faces the aperture-portion side. Because of this, the accelerating electrode is provided with a greater exposure area against the electron discharging portion consisting of a pn-junction than that of such an accelerating electrode provided for any of conventional electron discharging apparatuses.
A fourth method for manufacturing an electron discharging apparatus according to the present invention comprises the following steps:
a step of forming a pn-junction on the part of the surface of a semiconductor substrate;
a step of forming a first insulating film on said semiconductor substrate;
a step of forming a second insulating film on said first insulating film;
a step of forming an electrode film for forming an accelerating electrode on said second insulating film;
a step of patterning said electrode film and said second insulating film;
a step of removing said electrode film and said second insulating film formed on said pn-junction before forming an aperture portion;
a step of forming a side-wall electrode on a lateral wall of said aperture portion to cause said electrode film to be connected to said side-wall electrode;
a step of forming an accelerating electrode by means of said electrode film and said side-wall electrode;
a step of opening said electrode film formed on said pn-junction; and
a step of forming said aperture portion by way of extending itself.
According to the above-referred fourth manufacturing method, a step of forming a side-wall electrode to be connected to an electrode film is formed on a lateral wall of an aperture portion before forming an accelerating electrode by utilizing the electrode film and the side-wall electrode, and thus, the accelerating electrode is formed into a substantially inverse L-shaped configuration at a cross-sectional plane. And yet, inasmuch as the side-wall electrode corresponding to the substantially inverse L-shaped vertical wall portion faces the aperture portion, the accelerating electrode is provided with a greater exposure area against the electron discharging portion consisting of a pn-junction than that of such an accelerating electrode provided for any of conventional electron discharging apparatuses. Because of this, the accelerating electrode enables electrons discharged from the pn-junction to be accelerated to full extent.